<html>
  <head>
    <title>DeviceOrientation test</title>
    <script type="text/javascript">
      let eventTimeoutId; // To be set in start().

      function checkOrientationEvent(event) {
        // Return true iff the orientation is close enough to (1, 2, 3).
        return Math.abs(event.alpha - 1) < 0.01 &&
               Math.abs(event.beta  - 2) < 0.01 &&
               Math.abs(event.gamma - 3) < 0.01 &&
               event.absolute == false;
      }

      function onOrientation(event) {
        if (checkOrientationEvent(event)) {
          window.removeEventListener('deviceorientation', onOrientation);
          window.clearTimeout(eventTimeoutId);
          pass();
        } else {
          fail();
        }
      }

      function pass() {
        document.getElementById('status').innerHTML = 'PASS';
        document.location = '#pass';
      }

      function fail() {
        document.location = '#fail';
      }

      function failOnTimeoutIfNeeded() {
        let params = new URLSearchParams(location.search);
        let timeout = Number(params.get("failure_timeout"));
        if (timeout > 0)
          eventTimeoutId = window.setTimeout(fail, timeout);
      }

      function start() {
        window.addEventListener('deviceorientation', onOrientation);
        failOnTimeoutIfNeeded();
      }
    </script>
  </head>
  <body onLoad="start()">
    <div id="status">FAIL</div>
  </body>
</html>
